Method for modifying electrically nonconductive surfaces for electroless plating

ABSTRACT

ELECTRICALLY NON-CONDUCTIVE ORGANOPOLYMERIC SURFACES ARE PREPARED FOR ELECTROLESS PLATING BY INCLUDING IN THE ORGANOPOLYMERIC SURFACES AN EXTRACTABLE FILLER AND EXTRACTING THE FILLER FROM THE SURFACE PRIOR TO PLATING. IMPROVED ADHERENCY BETWEEN THE ELECTROLESSLY DEPOSITED METAL PLATE AND THE SURFACE IS EFFECTED.

United States Patent ABSTRACT OF THE DISCLOSURE Electricallynon-conductive organopolymeric surfaces are prepared for electrolessplating by including in the organopolymeric surface an extractablefiller and extracting the filler from the surface prior to plating.Improved adherency between the electrolessly deposited metal plate andthe surface is effected.

The present invention relates to methods for preparing electricallynon-conductive surfaces for electroless deposition of metallic filmswhich films exhibit improved adhesion to the surfaces so prepared.

Electrically non-conductive materials such as plastics, hard rubber,wood, ceramics, glass and the like are not adaptable to be platedelectrolytically. However, in the past few years extensive efforts havebeen put forth to find commercially acceptable methods forelectrolytically plating objects formed from these materials. Theseefforts have been undertaken in order to utilize inexpensive materials,such as plastics, in the place of metal. Also, materials such as plasticare more easily worked and can be formed easily into extremely diverseshapes. Metallized articles of the above nature are finding particularuse in the automobile industry Where parts of the interior and exteriortrim can be easily and inexpensively formed in extremely intricatedesigns and then coated with a metallic coating so as to simulate theappearance of metal articles.

One of the presently known processes for metallizing articles formedfrom electrically non-conductive materials is the electroless platingprocess. This process involves the catalytically induced reduction of ametal salt in a plating bath to form a metal plate. The basic steps ofthe process include the activation of the surface to be plated bydepositing on or including in the surface thereof catalytic metalparticles, such as palladium, followed by immersing the activatedsurface in a plating bath containing the metal to be plated in areducible ionic form and a reducing agent. The metal plate so formed maybe utilized as is, increased in thickness by further electroless platingor used as an electroconductive metallic film in standard electrolyticdeposition techniques to effect further metallic coating with the sameor different metals. While electroless plating is a well known process,the use of this process has been hampered by the difficulty in obtaininggood adhesion of the plate to the plated surface. Specifically, it hasbeen extremely difficult to sufficiently adhere electrolessly depositedmetal plates to electrically nonconductive surfaces, such as plastic, soas to allow the use of these items under a thermal cycle ranging from 20F. to about 200 F. Due to the vast differences in the thermal expansionratios of the metal and the base material, the deposited metal filmtends to delaminate when subjected to an extended thermal cycle if notsufficiently adhered to the base. The problem of adhesion is compoundedby the various types of base materials which can be used, and by thesize and intricacy of design into which these materials can be formed.

Patented Jan. 4, 1972 "ice The prior art has suggested abrading thesurface of the base in order to provide mechanical adhesion sites forthe metal film as a means for improving adhesion of the film through anextended thermal cycle. However, the use of mechanical treatments, suchas abrading, on intricately designed complex objects are essentiallynon-effective due to the nature of the item itself in that the intricatedesigns do not allow for easy, uniform and complete abrasion treatment.Chemical etching has also been utilized. However, this procedure is notsufficiently controllable so as to provide a plating surface having theuniform distribution of adhesion sites necessary to effect good overalladhesion of the electrolessly deposited metal plate. In the field ofplastics, the foregoing methods are generally ineffective on most typesof plastics. The problem of adhesion of the electrolessly deposited filmto plastic has dictated the use of certain plastics, such as ABS(acrylonitrile-butadiene-styrene). These materials are chemicallycorroded to apparently form a porous surface therein so as to improvethe adhesion of the metal plate to the surface. Other plastics, whichmight be more desirable for a specific use because of inherent physicaland chemical properties, or cost, cannot be treated in the same mannerto obtain the same results and, therefore, these plastics are notconsidered as base materials for electroless plating. Also, it isextremely difficult to treat bases formed from materials such as woodand ceramics to provide sufficient adhesion sites for the electrolesslydeposited metal film.

The method of the present invention provides means of preparingelectrically non-conductive surfaces for electroless plating so as toimprove the adhesion of the electrolessly deposited plate to the surfaceand which method is adaptable for use on plastics generally and onintricately shaped articles.

In accordance with the present invention, electrically non-conductivesurfaces are prepared for electroless plating by including, at least atthe surface thereof, an extractable filler and extracting the fillerfrom the surface prior to plating. By using controlled amounts of fillerand controlled filler particle size, the surface to be plated can beprovided with numerous microporous openings therein of controlled sizeand distribution. The microporous openings act as adhesive sites for theelectroless plate in that, theoretically, the metal fills the pores asthe plate is formed and thus the plate becomes mechanically anchored tothe surface being plated. Due to the large number of mechanical adhesionpoints made available by the method of the present invention,electroless plates characterized by improved surface adherency can beformed even on intricately shaped objects.

In one form of the invention, moldable base materials such as plastics,hard rubber and the like, e.g., an organopolymeric material, arecompounded to include an extractable filler material which is immisciblein the base material. Following the formation of the base material intoa shaped article, the surface of the article is treated so as to effectthe removal of filler material from the surface of the baseuA metallicfilm is then deposited over the so treated base which film ischaracterized by improved adhesion to the base due to the increasednumber of mechanical adhesion points available on the surface of thebase.

In another form of the present invention, the surface of a previouslyshaped article is coated with a plastic, hard rubber, or like material(organopolymeric material) which material has been compounded to includean extractable filler. Following solidification of the coating, thefiller is extracted and a metallic film is electrolessly deposited onthe coated surface which film is similarly characterized by improvedadhesion to the plated surface.

3 Plastics having some elasticity are advantageously used to form thecoatings as the elasticity can provide a buffer for the stressesencountered during expansion of the plate during the thermal cycle.Also, plastics having the same thermal expansion ratio as the metalplate can be advantageously used. The foregoing method is adaptable toprovide bases for electroless plating prepared from plastics in generaland also from other materials such as wood, glass, and ceramics whichbases have sufficient mechanical adhesion sites to provide for goodadhesion of the electrolessly deposited plate to the base.

In a further form of the present invention, the surface of a shapedarticle prepared from materials such as plastics, wood, glass andceramics is coated With a filmforming polymer dissolved in asolvent/non-solvent mixture which polymer is at the point of incipientprecipitation, and a porous film of polymer is formed on the base bycausing substantially complete precipitation of the polymer within thesolution by modifying the solvent/ non-solvent ratio.

Each of the foregoing methods of accomplishing the present invention areparticularly adapted to be used in effecting the electroless plating ofintricately shaped articles, and in particular, articles formed oforganopolymeric materials.

The extractable filler is preferably included within an organopolymericmaterial, e.g., a plastic or rubber material. The organopolymericmaterial can be utilized to form shaped articles for plating or it canbe used as a coating on a preformed base. In either case, the finallyprepared article for electroless plating has an organopolymeric surfaceincluding an extractable filler.

The organopolymeric material can be any one of the many known natural orsynthetic, plastic and rubber materials. These materials may be ofeither the thermoplastic or thermosetting type. The naturalorganopolymeric materials can be illustrated by natural rubber, hardwaxes and resinous gums, such as gum arabic and gutta-percha. Thesynthetic organopolymeric materials can be illustrated by the many knownmoldable and extrudable thermoplastic hydrocarbon and substitutedhydrocarbon polymers illustrated by polyethylene, polypropylene,polybutene, polyvinyl chloride, polystyrene, polyisoprene,polychloroprene, polybutadiene, styrene/butadiene co polymers thereofwith other ethylenically unsaturated monomers. Other forms of syntheticorganopolymeric materials can be illustrated by polyester polymers suchas the reaction product of ethylene glycol and maleic anhydride, andphthalic anhydride and propylene glycol; acrylates such as polymers andcopolymers of ethyl acrylate; methacrylates such as polymers andcopolymers of methyl methacrylate; epoxy such as the reaction productterephthalic acid and epichlorohydrin; alkyl polymers such as thereaction product of phthalic anhydride with glycerin or linseed oil;urea and melamineformaldehyde polymers; and polyurethane polymersillustrated by the reaction product of polyoxyalkylene glycols withtoluene diisocyanate. The polymers illustrated hereinbefore are but asmall part of the large number of organopolymeric materials which areadapted for use in the present invention. These materials are given asillustrative of the many known organopolymeric materials which can beused in the present invention and applicant is intended not to belimited thereto.

The foregoing list of organopolymeric materials can be used to formmolded or shaped bases having the extractable filler included therein orthey can be used to form a base which can be coated with anorganopolymeric material containing the extractable filler. Theselection of any one material for the formation of a shaped article forelectroless plating is dependent on the final characteristics desired inthe resultant product.

Many of the foregoing organopolymeric materials can also be utilized ascoatings in accordance with the present invention. In general, theorganopolymeric material selected for the coating should provide goodadhesion to the coated substrate along with suitable physical andchemical properties necessary for the intended use of the final product.The coatings can be applied from solvent solution using such solventsoluble polymers as the acrylates, or by the use of powder coatings orfluidized plastic coating techniques using such polymers as polyvinylchloride. The coatings can be used with equal effectiveness onnon-moldable bases such as wood, stone, glass and preformed ceramics, aswell as on moldable bases formed from organopolymeric materials. Thecoatings can also be used on metallic objects if it is desired to use ametal core for increased structural strength. As is obvious, any of theknown methods of applying coatings to base materials along with theattendant coating compositions are intended to be included Within thescope of the present invention.

The extractable filler is any material which can be incorporated in thematerial used to form the article desired to be electrolessly plated andwhich filler is immiscible in said material, and further, which fillerdoes not degrade or breakdown under the conditions of article formation.The filler can be of an organic or inorganic nature and can beextractable by means of dissolution, volatilization, and, in the case ofcertain metal salts, by chemical reduction. Preferably, the filler is ofsuch a nature as to be easily included within the base material and issuch as to afford easy extraction from the base without extensivechemical treatments, which treatments might damage the base article.Also the filler is preferably in such a form as to provide microporousopenings Within the surface of the base of a size ranging from about 0.1to about 1.0 microns.

Illustrative of inorganic fillers and their extracting agents (given inparenthesis) are: sodium, calcium, magnesium-carbonates (acids such asHCl, H HNO Al O -xH O, (acids such as H 80 ZnO (acids such as HCl, H 80HNO sodium silicates (water), glass in fiber form (HF), antimonyhydroxide, and the like. CaCO is a preferred inorganic filler.

Illustrative of organic fillers and their extracting agents (given inparenthesis) are: starch (enzyme solution), dimethyl sulfoxide (water),polybutadiene(acetone), polymethyl methacrylate(ketones such as methylethyl ketone, esters such as ethyl acetate, aromatic hydrocarbons suchas toluene), polyvinyl acetate(alcohols such as ethanol, ketones such asmethyl ethyl ketone, esters such as ethyl acetate, aromatic hydrocarbonssuch as toluene), polyvinyl alcohol (water), copolymers of vinylchloride/ vinyl acetate (ketones such as methyl ethyl ketone), mixturesof polyvinyl alcohol and dimethyl sulfoxide (water), copolymers of vinylformal and vinyl butyral (esters such as ethyl acetate, ketoncs such asmethyl ethyl ketone and cyclohexanone, alcohols such as butanol, andethers such as butyl Cellosolve), mixtures of polymethyl methacrylateand polybutadiene (esters such as ethyl acetate, ketones such as methylethyl ketone, aromatic hydrocarbons such as toluene), mixture ofpolymethyl methacrylate and polyethyl acrylate (esters such as ethylacrylate, ketones such as methyl ethyl ketone) and the like.

Illustrative of agents which can be extracted by volatilization arecamphor and iodine.

Illustrative of metal salts which can be reduced in situ to providemetallic particles which can act as catalytic agents for the electrolessplating reaction are: nickel carbonate, nickel oxide, iron oxide, andcarbonates and oxides of any metals which are catalytic for the platingreaction such as palladium oxide. The surface of the base is treatedwith an acid to leach out a portion of the metal salt leaving, in thepore, the remaining portion of the salt. Reduction of the remainingportion of the salt can be effected with a strong reducing agent such asconcentrated sodium hypophosphite or a borohydride such as methyl, ethylborane.

Similarly, pores having therein tiny particles of metal such as nickel,iron, copper, and the like which can act as catalytic sites for theelectroless plating reaction can be formed by incorporating the powderedmetal into the base and partially extracting the same with an acid.Also, metal particles such as nickel, zinc, iron, copper, aluminum andthe like can be incorporated in the base and completely leached out ofthe base with an acid to form the desired pores and the surface thenactivated utilizing the standard SnC1 /PdCl activation treatment. Thisactivation step can be eliminated with regard to the catalytic metals,e.g., nickel, iron, and copper, by utilizing, in the leaching solution,a complexing agent for the metal such as ammonia and amine complexingagents. A complex of the metal remains within the pores and can bereduced to free metal therein by immersing the base in a strong reducingagent, such as sodium hypophosphite or a borohydride such as methyl,ethyl borane to provide the catalytic sites necessary for electrolessplating.

The foregoing are given as illustrative of the numerous fillers whichcan be utilized in the process of the present invention, and applicantis intended in no way to be limited thereto.

In extracting fillers from organopolymeric materials, it is desirable toaccomplish the extraction in the presence of a solvent or swelling agentfor the polymer material. It has been found desirable to swell theorganopolymeric material used as the base so as to allow the solvent orextracting agent for the filler to enter into and extract the fillerfrom the base. The swelling solvent may be the agent used for extractingthe filler material or the swelling solvent can be in admixture with theextracting agent. Less desirably, the polymeric material can be insertedfirst into a solvent bath therefore and then into a bath of extractingagent. Illustrative of mixed solvent systems for a polymeric surfacesuch as polyvinyl chloride having a filler such as calcium carbonate aremethyl ethyl ketone for the polyvinyl chloride 'and hydrochloric acidfor the carbonate filler.

Slight surface roughening might also be necessary in order to expose theincluded filler for extraction and this can be accomplished by sandblasting, abrading, etc., as it well known to those skilled in the art.

Prior to effecting the electroless plating, it is necessary tothoroughly clean and degrease the substrate in that contaminants thereoncan detrimentally aifect the adhesion characteristics of the platedmetal film. The method of cleaning employed will depend on the nature ofthe substrate. In the case of plastics, spray washing with a detergentfollowed by a clear water rinse is eifective. If desired, mechanicalcleaning, such as sand blasting, canalso be used though this is notnecessary.

The cleaning operation can be a separate and distinct step in thepreparation of the substrate for plating or it can be part of the fillerextraction operation. If the filler is an organic solvent-solubleresinous material which is immiscible with the base material, washing inan organic solvent can be sufiicient to effect the degreasing and theextraction. In using a volatilizable filler, the use of elevatedtemperature to effect removal of the filler will also efiect removal ofsurface moisture and other contaminants subject to volatilization.

Following the cleaning step, the base is sensitized, e.g., depositingcatalytic metal particles on the surface of the base. Sensitization bychemical reduction generally involves two steps. The first requires theformation of a film or deposits of stannous chloride on the poroussurface and within the pores. This is accomplished by the immersion ofthe base in an acidic stannous chloride solution generally containingabout 30 grams of stannous chloride and milliliters of concentratedhydrochloric acid per liter of water. The immersion time need be only afew seconds and slight agitation is recommended to insure completecontact especially in the case of intricately shaped articles. Thearticle is then water washed to remove excess stannous chloride so as toprevent its transfer to and the contamination of the second bath. Twowashings of from about 20 to about 30 seconds have been found sufiicientto remove any excess stannous chloride without removing the desiredsurface deposit. In more intricate articles, subsequent washings can beemployed if desired to insure suflicient removal of the stannouschloride. The washed article having deposits of stannous chloridethereon is then immersed in a palladium chloride bath. The stannous ionsare oxidized to stannic ions and the palladium ions are reduced to freemetal. Following this treatment, the base is again washed as before toremove all the stannic ions and any remaining palladium chloride so asnot to contaminate the electroless plating bath.

The surface of the base can also be sensitized or pretreated by theinclusion of metal particles in the base material prior to formation orapplied to the surface subsequent to formation. Catalytic quantities ofelectro-conductive material such as nickel, aluminum, iron, cobalt,chromium, and the like in a finely divided state can be compounded intothe base material prior to molding and exposed by mechanical abrading.The particles can also be applied by dusting, utilizing, dipping, airblast or other techniques adapted for such application. In the dustingoperation, a moistened or sticky surface can facilitate application.This can be accomplished by the application of an adhesive to thesurface or by immersing a plastic article in a solvent therefor. Furtherdetails of this can be obtained in US. Pat. 2,690,401.

Sensitization can also be accomplished by using as the filler areducible metal salt and reducing the salt situ to form pores in thesurface of the base having thereon particles of catalytic metal asdiscussed hereinbefore. Also, and after filler extraction, the base canbe immersed in an electroless nickel plating solution to wet theinterior of the pores. The so treated base can then be inserted in aconcentrated hypophosphite solution to reduce the nickel ion to freemetal within the pores, which metal can then act as the catalytic metalfor the electroless plating reaction.

Following the pretreatment of the base, the base is immersed in theelectroless plating solution which can be acidic or alkaline. Ingeneral, the plating solution is a bath containing the metal to beplated in ion form, a reducing agent and in an acidic solution, abuffer. In an alkaline solution, an agent such as ammonium hydroxide orchloride is used to maintain the pH on the alkaline side. Nickel isgenerally used as the plating metal in that it provides a good metallicfilm and can be electrolytically plated following the electrolessplating. Other metals such as cobalt, chromium, copper, gold, iron,silver, vanadium and, with proper solutions, alloys such as brass andcobalt-nickel alloys can also be used. For use with the nickel, areducing agent such as sodium hypophosphite has been found to beeffective. Other reducing agents and complexing systems as shown in theart are also useable. The buffering material for the acid solution canbe any material which will provide the bulfering efiect without undulyaffecting the plating bath. Mention can be made of soluble salts ofshort chain aliphatic monocarboxylic acids having an ionization constant(pKa) greater than about 4.5 such as acetic acid, butyric acid,propionic acid and the like. The ratio of reactants in the bath so as toprovide a desired ratio of ions therein can be determined for eachsystem so as to provide effective plating. The immersion of the base inthe plating bath is for a time sufficient to effect the plating of thedesired film on the base. Temperature, agitation and other factors whichmay affect the plating can be determined in each situation.

Following the application of the initial electrolessly deposited metalfilm, the base can be subjected to further electroless metal deposition,especially of other metals, or plated electrolytically with such metalsas copper, nickel, zinc or chromium. The amount of plating and the typedepends on the final use of the product and the thickness of metaldesired on the base. In some instances, it may be required to depositlarge amounts of metal on the base to insure that the pores arecompletely filled and the overall surface of the metal film is flat.

The invention will be illustrated in the examples which follows:

EXAMPLE 1 Plaques for electroless plating are prepared using a mediummolecular weight polyvinyl chloride homopolymer (R.V. 2.11) compoundedwith:

TAB LE I Amount in parts/ hundred Sample Filler of PVC 1 "{PoJlymethylmethacrylate/polyethyl acrylate mix- 10 ure. Cis-polybutadicne lPolymethyl mothacrylate/polyethyl acrylate mix- 10 ure.Cis-polybutadiene... 10 Calcium carbonate 10 ABS (Blendex 401) 20 ABS(Blendex 101).- 20 Calcium carbonate 10 Cis-polybutadiene... 20 Calciumcarbonate- 10 Cis-polybutadiene .1. 20 6 Phenolic antioxidant. Calciumcarbonate 10 The plaques are pretreated as follows:

TABLE IL-P RETREA TMENT Cold Temp, Time/ water 0. min. rinses 1 AcetoneRT 2 2 2---- HNOa 1 1-.- 65 10 2 3".-- Hot water 65 5 1 4..."sensitizing, RT 1 2 5. Activation, PC1012 RT 2 Following pretreatment,the plaques are immersed in an electroless plating solution maintainedat 60 C. and at a pH of 5.7 for minutes, the solution having thefollowing composition:

1 A nonionic surfactant having the formula:

0 (O C HQDOH C4H CH CHzO P sold under the name of VICTAWET-IZ Goodadherent nickel plates are obtained on each sample plaque of Table I.

EXAMPLE 2 Plaques of the Sample 3 type of Table I are pretreated underthe following conditions:

TABLE IV.P RET REATMENT Cold Temp, Time] water 0. min rinses 3.Elcctroless nickel Solution A 4. 40% Sodium hypophosphite solution.

Following pretreatment, the plaques are immersed in electroless nickelplating Solution A for 10 minutes, which solution is maintained at 60 C.Good nickel plates are obtained.

TABLE VI.-P RETREATMENT AND PLATING CYCLE Cold.

Temp. Time/ water 0. min. rinses 1 Alkaline cleaner 6O 5 2 2. Methylethyl ketone RT 2 2 3.- HNO3221 60 15 2 4.-- H2SO415 60 10 2 5...-.-HC1l5%-. RT 10 2 6-..... Dilute SnClz 60 3 1 7. Sensitization. SnCl2 RT1 2 8..- Activation, PdClz RT 2 9. Elcctroless nickel plating SolutionA- 60 10 2 Good plates are obtained on all plaques. Sample plaque No. 2was subjected to a thermocycle heat stability and adhesion test whichencompasses alternate heating and cooling of the plated sample, theupper temperature being 210 F. and the lower temperature being -50 F.Complete particulars on this test can be found at page 540 of the Trans.J. Plastics Inst., June 1967, (Britain). After four thermocycles, nopeeling or blistering was observed.

EXAMPLE 4 Plaques are prepared for electroless plating and plated asfollows:

TABLE VII.PLAQ,UES

Amount Sample by weight 1 .{PVC (R.V. 2.11).-.. ABS (Blender 401) 100PVC R.V. 2.11 200 4 100 Polyvinyl formal 30 5 PVC (R.V. 2J1) 100Polyvinyl formal 40 6 -{PVC (R.V. 2.11) 100 Calcium carbonate 20 TABLEVIIL-PRETREATMENT AND PLATING CYCLE 9 EXAMPLE Polyvinyl chloride plaquesare knife coated with one of the following coating compositions andplated as follows:

TABLE IX Carrier Filler Amount 1--. PVC/PVA copolymer VYHD) DimethylSulfoxide. 90/10 1... PVC/PVA copolymer VYHD) Polylvinyl methyl 90/10 eer. 3... PVG/PVA copolymer (VYHD) Cis-polybutadiene..-- 90/10 4...PVC/PVA copolymer (VYHD) Monomethyl ester of 90/10 a vinyl methylether/maleic anhydride copolymer.

AND PLATING CYCLE Cold TABLE X.P RETREATMENT All coated plaques areplated with good nickel plates. Plaques 1 and 2 are provided with amirror-like uniform and adherent nickel plate. All of the above plaqueswere subjected to and passed a scratch test and an adhesive tape test.The scratch test is conducted by scribing a line on the surface of thenickel plate and then another line at an acute angle to the first. Thetest is to determine scratch adhesion by observing the amount of plateremoved from the surface at the juncture of the two intersectingscratches. The adhesive tape test (or Scotch tape test) is a furtheradhesion test which is conducted by adhering a piece of tape overintersecting scratches obtained in the manner described for the scratchtest and lifting the tape from the scratched plated surface. The testdetermines the adherence of the metal plate to the base relative to theadhesive bond of the tape.

EXAMPLE 6 Plaques of polyvinyl chloride are coated with solutions of thefollowing compositions and plated as follows:

1 (TH F tetrahydrofuran) Good plates are obtained from all plaques.

What is claimed is:

1. A method for preparing a polyvinyl chloride surface for electrolessplating comprising:

(a) admixing a solvent-soluble extractable filler with a polyvinylchloride;

(b) forming the admixture obtained from step (a) into a shaped article;

(0) immersing said shaped article into a swelling solvent for polyvinylchloride; and

(d) dissolving said solvent-soluble extractable filler from said shapedarticle prior to plating to an extent sufficient to provide cavitiesupon the surface of said shaped article of a size ranging between about0.1 to 1.0 microns.

2. Method as recited in claim 1 wherein said filler is an inorganicfiller.

3. Method as recited in claim 2 wherein said inorganic filler isselected from the group consisting of calcium carbonate and aluminumoxide.

4. Method as recited in claim 1 wherein said filler is anorganopolymeric material.

5. Method as recited in claim 4 wherein said organopolymeric material isselected from the group consisting of an acrylonitrile/butadiene/styrenecopolymer, polybutadiene, and polyvinyl acetal polymers.

6. Method as recited in claim 1 wherein said surface to be plated is afilm of polyvinyl chloride coated on a formed base.

7. The method of claim 1 wherein said swelling solvent is methyl ethylketone.

References Cited UNITED STATES PATENTS 2,806,256 9/1957 Smith-Iohannsen117-63 2,826,509 3/1958 Sarbach 117-1355 3,011,920 12/1961 Shipley117-47 R 3,202,733 8/1965 Shauss 156-3 3,370,974 2/1968 Hepfer 117-47 R3,399,268 8/ 1968 Schneble ct a1 117-47 R ALFRED L. LEAVITT, PrimaryExaminer J. A. BELL, Assistant Examiner U.S. Cl. X.R.

1 were 8M1 PATENT QFFEQE (5/09) QEHTL'FCAEE or sorrmcrmw l-atent No 5,652 ,704 Dated January 4, 1972 Inventor s Miguel CollPalagos It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 8, Example '5, Tablev V, Sample 3 should read --Graft Copolymerof polyvinyl chloride 90 and polybutadiene lO Column 9, Example 6,"Table IX" should be changed to Table XI-- 1 The following referenceswere not cited and should be inserted therein: 2,686,751 8/1954 Wainer106 288(1) 2,819, 175 1/1958 Dithmar 106 288(1) 5, 151,12o 5/1969Weisenberger' 117 47 (R) 5,466,252 9/1969 Francis e-t al 20 5o 5, +67,51o 9/1969 Shick 117 47 (R) Signed and sealed this 20th day of June 1972.

(SEAL) Attest:

EDWARD M.FLETCI IER',JR. ROBERT GOTTSCHALK Attesting OfficerCommissioner of Patents

